Evidence for an electromechanical process of intracochlear origin has been acquired by means of alternating current injection in scala media. A direct acoustic emission appears at the same frequency as the electrical current. In addition, the injected current modulates the sound pressure level of an input acoustic tone. We propose to characterize empirically this effect in the electrical and acoustical stimulus domains. We plan to explore the nature of the effect and its relation to auditory-nerve responses, using a variety of experimental manipulations. These include direct current injection in scala media, stimulation of cochlear efferents, two-tone suppression, cochlear temperature, ion-substitution, and sounds which produce acoustic trauma. The latter experiments involve SEM studies which will likely show concomitant damage to cochlear hair cells. As a working hypothesis, we believe that outer hair cells' (OHC) function includes not only transduction but also an active role in cochlear mechanics. The OHCs possess few, if any, afferent synapses; and yet OHC transduction does occur, as evidenced by the cochlear microphonic. We think that OHC transduction is involved in an electromechanical feedback process which affects basilar membrane response. We propose to construct computer simulations as the analytic embodiment of this idea. We intend to compare new data with model results.